Crude oil - 18 meters, roughly the length of a humpback whale.Coal - 10 meters, about the length of a school bus.Wood - 7 meters, about the width of a two car garage.Below is a list of other fuels compared to coal to figure out the energy per distance to compare other fuels to coal. This makes the energy available in that same mass of uranium equal to the distance between Vancouver, British Columbia to Saskatoon, Saskatchewan(Figure 2). How far can you go?Įnergy sources do not give up their energy in the same ways, but assuming they could, how far would each move a vehicle? To find out, coal can be used as a base-line, if the amount of energy in a particular mass of coal equal to 10 meters - the length of a school bus. Table 1: The energy density(MJ/kg) of a variety of different fuels. Household heating, Electricity generation Gasoline mixture, Alcohol, Chemical products The table below shows the energy density for a variety of common fuels.įor a visual representation of these values, Figures 1 and the graph to the right show comparisons of energy densities of different fuels. When the fuels come directly from nature (like crude oil) they are primary fuels when the fuels have to be modified so they can be used (like gasoline) they're referred to as secondary fuels. These materials are known collectively as fuels, and all of these fuels are used as energy sources for a variety of systems. Many different materials can store energy, ranging from food, to diesel, to uranium. Visit energy density vs power density for more information and examples. Typically having a high energy density goes along with a low power density. This knowledge is contained in a substance's power density, which describes the rate at which its energy can be put out.
Having a high energy density does not give information on how quickly this energy can be used. Gravimetric energy density can also be referred to as specific energy. Gravimetric energy density - how much energy a system contains in comparison to its mass typically expressed in watt-hours per kilogram (Wh/kg), or Megajoules per kilogram (MJ/kg).Volumetric energy density - how much energy a system contains in comparison to its volume typically expressed in watt-hours per liter (Wh/L) or Megajoules per liter (MJ/L).Įnergy density is generally expressed in two ways, although the first is more common: In scientific equations, energy density is often denoted by U. When calculating the amount of energy in a system most often only useful or extractable energy is measured. These reactions are nuclear, chemical, electrochemical and electrical. Ī material can release energy in four types of reactions. The higher the energy density of a system or material, the greater the amount of energy it has stored. Energy density can be measured in energy per volume or per mass. Įnergy density is the amount of energy that can be stored in a given system, substance, or region of space. An XKCD comic showing the comparative energy density of Uranium.
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